Long range target identification plays an important role in defense and space awareness. Any information that may be obtained from a remote target can be potentially used to establish specific features of the target and/or classify the target. An example of such information is the rotation characteristics of the target, including whether the target is rotating, the magnitude of that rotation, and the axis of that rotation. For example, a target in flight may be observed to exhibit rotation if spinning about an axis and/or experiencing a change in flight direction. This rotation information alone may be sufficient to determine specific features of the target. Alternatively, this rotation information can be used in combination with other, more sophisticated, imaging approaches (e.g., inverse synthetic aperture and tomography) to determine specific features of the target.
While radar has been employed for measurement of target rotation characteristics, radar sensing does not perform well with dynamic targets that rotate relatively slowly. For example, a radar requires about 10 minutes to resolve the rotation characteristics of a target exhibiting an angular velocity of 1 mrad/sec. Such a timeframe may be unacceptably long for certain applications of interest (e.g., target identification).
Accordingly, there exists a need for improved techniques for measurement of a target's rotation characteristics at longer ranges.